Particulate filter regeneration method of diesel hybrid vehicle

ABSTRACT

A method of regenerating a particulate filter of a diesel hybrid vehicle includes determining whether a regeneration condition for a particulate filter that filters particulate matter in an exhaust gas discharged from an engine may be satisfied, entering a mode for increasing the temperature of the exhaust gas when the regeneration condition may be satisfied, increasing output torque of the engine to increase the temperature of the exhaust gas, determining redundant torque by subtracting demand torque from the increased output torque of the engine, generating electricity by a motor by using the redundant torque, and storing the electricity generated by the motor in a battery.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to and the benefit of Korean Patent Application No. 10-2014-0170351 filed on Dec. 2, 2014, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of regenerating a particulate filter of a diesel hybrid vehicle which can reduce fuel consumption using a diesel engine and a driving motor and can reduce environmental pollution by decreasing a discharge amount of particulate matter in exhaust gas.

2. Description of Related Art

In general, as methods of regenerating diesel particulate matter, there are a passive type that uses only exhaust gas for regeneration without a specific heat source and a forcible type that burns particulate matter by forcibly supplying a chemical heat source.

As for the passive type, there are a type of using an oxidation catalyst filter which burns particulate matter after reducing a generation temperature of the particulate matter by mixing a metal such as iron (Fe), cerium (Ce), copper (Cu), and platinum (Pt) with a fuel, or coating a filter with a precious metal, and a type using a particulate filter which directly filters particulate matter.

The type using a particulate filter collects particulate matter and then directly burns it or heats it up to a temperature where it can be burned. Further, in a common rail type of diesel engine, fuel is sprayed and burned in the latter portion of the exhaust process, thereby increasing the exhaust gas temperature and accordingly burning the collected particulate matter.

Recently, a diesel hybrid vehicle equipped with a driving motor combined with a diesel engine has been studied and developed, in which the driving motor supports the engine using electrical energy stored in a battery or only the driving motor is used for driving, so fuel consumption can be considerably reduced.

Meanwhile, a process of increasing the temperature of an exhaust gas is performed to regenerate a particulate filter in the diesel hybrid vehicle, but when post-injection is performed in order to increase the temperature of an exhaust gas, as described above, there is little change in output and fuel consumption increases instead.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing a method of regenerating a particulate filter in a diesel hybrid vehicle which increases the temperature of an exhaust gas to regenerate a diesel particulate filter, but is capable of reducing fuel consumption and saving an operation cost by recovering it.

An exemplary embodiment of the present invention provides a method of regenerating a particulate filter of a diesel hybrid vehicle which includes: determining whether a regeneration condition for a particulate filter that filters particulate matter in an exhaust gas discharged from an engine is satisfied; entering a mode for increasing the temperature of the exhaust gas when the regeneration condition is satisfied; increasing output torque of the engine to increase the temperature of the exhaust gas; calculating redundant torque by subtracting demand torque from the increased output torque of the engine; generating electricity by means of a motor by using the redundant torque; and storing the electricity generated by the motor in a battery.

A main injection amount of the injector may be increased to increase the output torque.

The motor may be an HSG (Hybrid Starter and Generator) that starts the engine or generates electricity using torque from the engine.

The motor may be a driving motor that transmits torque to driving wheels, together with the engine.

The electricity generated by the motor may be stored in the battery.

The regeneration condition for the particulate filter may be determined on the basis of a front-rear pressure difference of the particulate filter or a driving distance.

The engine may rotate front wheels and the motor may rotate rear wheels.

The engine may be connected with the motor through an engine clutch and the motor may rotate front wheels through a transmission.

The method may further include performing post-injection if the temperature of the exhaust gas does not reach a predetermined level.

A diesel hybrid vehicle according to an exemplary embodiment of the present invention may include a controller for performing the method of regenerating a particulate filter of a diesel hybrid vehicle.

In order to achieve the object, when the regeneration condition for a diesel particulate filter is satisfied under a normal operation condition, it is possible to increase output torque of an engine and regenerate the diesel particulate filter by increasing the temperature of the exhaust gas, by increasing the main injection amount.

Further, the redundant torque between the increased output torque and the demand torque is recovered as electrical energy through an HSG or a driving motor and stored in a battery, so it is possible to easily reduce fuel consumption.

Further, the main injection is increased to regenerate the diesel particulate filter, but when the temperature of the exhaust gas does not reach a predetermined temperature, the temperature of the exhaust gas can be stably corrected by controlling post-injection of the injector.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing characteristics of fuel injection of an injector in a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

FIG. 2 is a graph showing operation characteristics of a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

FIG. 3 is a schematic diagram showing the configuration of an engine of a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

FIG. 4 is a schematic diagram showing the configuration of a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

FIG. 5 is a schematic diagram showing the configuration of a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

FIG. 6 is a flowchart illustrating a method of regenerating a particulate filter of a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

An exemplary embodiment of the present invention will hereinafter be described in detail with reference to the accompanying drawings.

FIG. 1 is a graph showing characteristics of fuel injection of an injector in a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the horizontal axis is a rotational angle (time) of the crankshaft of an engine 315 and the vertical axis shows the characteristic of the amount of fuel injected from an injector 300.

As shown in the figure, the injector 300 sequentially injects fuel at predetermined times, and the injection includes first pilot injection 100, second pilot injection 105, main injection 110, first post-injection 115, and second post-injection 120.

The main injection 110 actually contributes to output torque, and the pilot injection and the post-injection reduce vibration noise and control the characteristic (e.g., temperature) of exhaust gas while contributing little to the output torque. However, when a large amount of fuel is injected in the main injection 110, the output torque and the temperature of an exhaust gas may both be increased.

FIG. 2 is a graph showing operation characteristics of a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the horizontal axis shows a rotational speed of an engine 315 and the vertical axis shows BMEP of the engine 315. In an exemplary embodiment of the present invention, when a regeneration condition for a diesel particulate filter (DPF) 305 is satisfied, the current BMEP (about 8) is optionally increased to a setting value (about 12), thereby increasing load or output (torque) of the engine 315.

This state may be applied to idling of the engine 315 or a rotational sped higher than an idle rotational speed, but when torque or load increases, the RPM of the engine is maintained at the level or is not specifically corrected.

In an exemplary embodiment of the present invention, the main injection amount of the injector 300 is increased to increase the BMEP, redundant torque between increased output torque and demand torque is calculated, and a hybrid starter and generator (HSG) 500 or a driving motor 520 generates electricity by using the redundant torque. The electricity generated by the HSG 500 or the driving motor 520 is stored in a battery 490 through an inverter.

FIG. 3 is a schematic diagram showing the configuration of an engine of a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

Referring to FIG. 3, an engine system includes an engine 315, an intake line 302, an intercooler 310, an injector 300, an exhaust line 320, a diesel particulate filter 305, a low-pressure EGR line 350, a low-pressure EGR cooler 355, a high-pressure EGR line 340, a high-pressure EGR cooler 345, and a turbocharger 330, in which the turbocharger 330 includes a turbine 332 and a compressor 334.

External air is taken inside through the intake line 302, the compressor 334 of the turbocharger 330 compresses the air, the intercooler 310 cools high-temperature compressed air, the injector 300 injects fuel into a combustion chamber, the injected fuel is mixed and burned with air, and an exhaust gas is discharged through the exhaust line 320.

The diesel particulate filter 305 collects particulate matter contained in the exhaust gas and removes the collected particulate matter by burning it under a predetermined high-temperature condition. Further, the turbine 332 disposed in the exhaust line 320 is rotated by the exhaust gas and operates the compressor 334.

The diesel particulate filter 305 is equipped with a front-rear differential gear device pressure sensor, so it can detect a front-rear pressure difference and the diesel particulate filter can be regenerated on the basis of the detected pressure difference or an operational condition of the engine, that is, a driving distance.

The low-pressure EGR line 350 is divided at the downstream side from the diesel particulate filter 305 and connects with the upstream side from the compressor 334, while the high-pressure EGR line 340 is divided at the upstream side from the turbine 332 and connects with the downstream side from the intercooler 310.

A low-pressure EGR valve and a high-pressure EGR valve are disposed in the low-pressure EGR line 350 and the high-pressure EGR line 340, respectively, so they can control a recycling exhaust gas.

FIG. 4 is a schematic diagram showing the configuration of a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

Referring to FIG. 4, a diesel hybrid vehicle includes an HSG 500, an engine 315, an injector 300, a diesel particulate filter 305, an engine clutch 510, a transmission 530, a front differential gear device 540, a driving motor 520, a rear differential gear device 400, a battery 490, and a controller 550.

In an exemplary embodiment of the present invention, the controller 550 may be achieved by one or more microprocessors that are operated by a predetermined program, and the predetermined program may include a series of commands for performing a method according to an exemplary embodiment of the present invention.

The HSG 500 is coupled to the engine 315 and starts the engine 315 through a belt or a gear or generates electricity using torque from the engine 315, and the battery 490 is charged with the electricity through an inverter.

The engine 315 generates torque using fuel injected from the injector 300, and the burned exhaust gas is discharged outside through the diesel particulate filter 305.

The engine clutch 510, the transmission 530, the front differential gear device 540, and front wheels are sequentially mounted on an output shaft of the engine 315, and the torque from the engine 315 is transmitted to the front wheels through the engine clutch 510, the transmission 530, and the front differential gear device 540.

The engine clutch 510 selectively transmits the torque from the engine 315 to the transmission 530, the transmission 530 controls a gear ratio, and the front differential gear device 540 distributes torque to the left and right wheels.

Separate from the engine 315, the driving motor 520 is disposed to rotate rear wheels through the rear differential gear device 400. Further, in regenerative braking, the driving motor 520 generates electricity using torque transmitted from the rear wheels and the generated electricity is stored in the battery 490 through the inverter.

The controller 550 controls the engine 315, the injector 300, the HSG 500, the engine clutch 510, the transmission 530, the driving motor 520, the inverter, and the battery 490 so that the diesel hybrid vehicle normally operates.

FIG. 5 is a schematic diagram showing the configuration of a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

Referring to FIG. 5, a diesel hybrid vehicle includes an HSG 500, an engine 315, an injector 300, a diesel particulate filter 305, an engine clutch 510, a driving motor 520, a transmission 530, a front differential gear device 540, front wheels, a battery 490, and a controller 550

The HSG 500 is coupled to the engine 315 and starts the engine 315 through a belt or a gear or generates electricity using torque from the engine 315, and the battery 490 is charged with the electricity through an inverter.

The engine 315 generates torque using fuel injected from the injector 300, and the burned exhaust gas is discharged outside through the diesel particulate filter 305.

The engine clutch 510, the driving motor 520, the transmission 530, the front differential gear device 540, and the front wheels are sequentially mounted on an output shaft of the engine 315, and the torque from the engine 315 is transmitted to the front wheels through the engine clutch 510, the driving motor 520, the transmission 530, and the front differential gear device 540.

The engine clutch 510 transmits torque from the engine 315 to the driving motor 520, the driving motor 520 adds its torque and transmits it to the transmission 530, the transmission 530 controls a gear ratio, and the front differential gear device 540 distributes the torque to the left and right wheels.

The driving motor 520 supplements the torque from the engine 315 or may rotate the front wheels through the transmission 530 without the torque from the engine 315.

The controller 550 controls the engine 315, the injector 300, the HSG 500, the engine clutch 510, the transmission 530, the driving motor 520, the inverter, and the battery 490 so that the diesel hybrid vehicle normally operates.

FIG. 6 is a flowchart illustrating a method of regenerating a particulate filter of a diesel hybrid vehicle according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the controller 550 determines whether a regeneration condition is satisfied in step S600. The regeneration condition may be satisfied when the front-rear pressure difference of the diesel particulate filter 305 is greater than or equal to a predetermined pressure. In addition, the regeneration condition may be satisfied when the driving distance of the diesel hybrid vehicle becomes a predetermined distance. The controller 550 enters a mode for increasing the temperature of an exhaust gas to remove particulate matter collected by the diesel particulate filter 305 in step S610.

The controller 550 executes a mode for increasing the output torque of the engine 315 in step S620 and the main injection amount of the injector 300 is increased in step S630. In step S640, a redundant torque is calculated by subtracting demand torque from the increased output torque of the engine 315.

In step S650, the HSG 500 or the driving motor 520 generates electricity using the redundant torque and the generated electricity is stored in the battery 490 through the inverter.

Further, in step S660, if the temperature of the exhaust gas does not reach a predetermined level, the temperature of the exhaust gas is corrected, in which the injector 300 may be made perform post-injection. Finally, in step S670, the diesel particulate filter 305 is regenerated and the controller 550 returns to a normal mode.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. A method of regenerating a particulate filter of a diesel hybrid vehicle, comprising: determining whether a regeneration condition for the particulate filter that filters particulate matter in an exhaust gas discharged from an engine is satisfied; entering a mode for increasing a temperature of the exhaust gas when the regeneration condition is satisfied; increasing output torque of the engine to increase the temperature of the exhaust gas; determining a redundant torque by subtracting a demand torque from the increased output torque of the engine; generating electricity by a motor by using the determined redundant torque; and storing the electricity generated by the motor in a battery.
 2. The method of claim 1, wherein a main injection amount of an injector is configured to be increased to increase the output torque.
 3. The method of claim 1, wherein the motor is a Hybrid Starter and Generator (HSG) that starts the engine or generates the electricity using torque from the engine.
 4. The method of claim 1, wherein the motor is a driving motor that transmits torque to driving wheels, together with the engine.
 5. The method of claim 1, wherein the regeneration condition for the particulate filter is determined on a basis of a front-rear pressure difference of the particulate filter or a driving distance.
 6. The method of claim 4, wherein the engine rotates front wheels and the motor rotates rear wheels.
 7. The method of claim 4, wherein the engine is connected with the motor through an engine clutch and the motor rotates front wheels through a transmission.
 8. The method of claim 1, further comprising performing post-injection when the temperature of the exhaust gas does not reach a predetermined level.
 9. The method of claim 1, wherein, in the increasing the output torque of the engine, RPM of the engine is not corrected.
 10. A diesel hybrid vehicle comprising a controller for performing the method of claim
 1. 